Such a connection is described in PCT Published Patent Application No. WO 99/66177, where the actuating element is formed by a differential piston that may be guided in an axially movable manner within a pressure region, able to be pressurized by a pressure medium, of a cylinder arranged in an actuator housing and surrounds the shaft ends of the gas exchange valve. The pressure region may include a top and a bottom working chamber within the cylinder, which may be axially spaced by the differential piston and may be bordered by its two end faces. Depending on the pressurization of the two working chambers, the differential piston may slide up and down within the cylinder. The connection of the shaft end of the gas exchange valve and the differential piston may be achieved by wedge pieces that are radially pressed against the shaft ends by a slipped-on conical tensioning sleeve having a complementary wedge angle and rest axially on the differential piston, thereby making it possible for annular protuberances formed on the radially internal peripheral surface of the wedge pieces to intermesh in a form-locking manner with annular grooves on the outer periphery of the shaft end.
The connection between the shaft ends of the gas exchange valve and the differential piston may be arranged completely within the hydraulically sealed cylinder in the top working chamber that is bordered at the extremity by a cylinder bottom that is one piece with the cylinder. The connection may, therefore, be first accessible from the outside when the hydraulically sealed cylinder or the entire actuator housing is first removed. In the course of periodical assembly or disassembly of the connection, e.g. for repair purposes, the hydraulic circuit may, therefore, need to be opened, and there may be a danger of dirt and air penetrating the hydraulic system. Moreover, seals may be damaged when the actuator housing is installed at a tilt with respect to the differential piston.